The United Nations Security Council has called for a prompt, impartial, credible and transparent investigation of the raid on a humanitarian aid convoy by Israeli navy commandos.
At least nine people, mostly Turkish human-rights activists, were killed in the raid.
After a marathon emergency session, 10 hours of it behind closed doors, the council formally condemned the raid and called for the immediate release of ships and civilians held by Israel after the raid.
Britain, France, Russia and China have called for the blockade of Gaza to be lifted - and the council's other permanent member, the US, has hinted at agreeing to it too.
A wave of global outrage has arisen over the incident.
Commandos 'acted in self-defence'
Israel's deputy ambassador to the UN told the council that Israeli commandos acted in self-defence against people with links to Hamas.
Israel says its forces were shot at and attacked with bars and knives - but the aid campaigners say the troops came on board shooting.
Palestinian president Mahmoud Abbas has described the raid as a massacre and Turkey's foreign minister, Ahmet Davutoglu, has called Israel's actions "murder by a state".
But Israeli government spokesperson Marc Regev says the San Marino Memorandum allows a country to intercept a ship in international waters when there is a declared blockade and vessels have been warned not to enter the area.
He says the maritime blockade of Gaza is in place because the Hamas movement in Gaza is getting rockets and missiles from Iran and Syria that are used to attack Israeli civilians.
Israeli Prime Minister Benjamin Netanyahu, who is in Canada, called off a trip to Washington on Tuesday to return to Israel and deal with the crisis.
Earlier, his office said he expressed his "full backing" for the military involved in the raid. Mr Netanyahu says he regrets the loss of life, but his troops were attacked first.
10,000 tonnes of aid
The BBC reports a flotilla of six ships, carrying 10,000 tonnes of aid, left the coast of Cyprus on Sunday and had been due to arrive in Gaza on Monday.
Israel had repeatedly said the boats would not be allowed to reach Gaza, calling the campaign a "provocation intended to delegitimise Israel".
It says it allows about 15,000 tonnes of humanitarian aid into Gaza every week, but the UN says that's less than a quarter of what is needed.
Three of the six ships have now been towed to the port of Ashdod. Israeli public radio has reported that 480 activists have been detained in prison there, while another 48 will be expelled.
The convoy was organised by the Free Gaza movement, which is based in Turkey. Israeli deputy foreign minister Daniel Ayalon says the group has ties to terror groups, including al Qaeda.
